Industrial Crops and Products 84 (2016) 7–12 Contents lists available at ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop Effects of municipal sludge and treated waste water on biomass yield and fiber properties of kenaf (Hibiscus cannabinus L.) C. Ververis a,∗ , N.S. Christodoulakis a , R. Santas b , Ph. Santas b , K. Georghiou a a National and Kapodistrian University of Athens, Faculty of Biology, Department of Botany, Panepistimiopolis, Athens GR 157 84, Greece b Oikotechnics Institute, Kefallenias 50, Ano Helioupolis GR 163 42, Greece a r t i c l e i n f o Article history: Received 2 June 2015 Received in revised form 21 January 2016 Accepted 24 January 2016 Keywords: Kenaf Sewage sludge Municipal waste Biomass Fiber properties a b s t r a c t Kenaf (Hibiscus cannabinus L.) was experimentally cultivated with the use of digested, dried sewage sludge (130 t/ha) and water from a municipal Sewage Treatment Plant (STP) in order to assess their potential to replace conventional fertilization (100 kg N/ha, 75 kg P 2 O 5 /ha and 75 kg K 2 O/ha) and irrigation. Tap water and treated wastewater were used for irrigation in quantities corresponding to 6500 m 3 /ha. Four different treatment combinations were applied as follows: (a) wastewater irrigation and conventional fertilization, (b) wastewater irrigation and sewage sludge fertilization, (c) tap water irrigation and sewage sludge fertilization, and (d) tap water irrigation and conventional fertilization. The dry plant biomass collected in the final harvest (140 days after plant emergence) from the four treatment plots was 12.3 t/ha, 12.6 t/ha, 12.4 t/ha and 12.8 t/ha respectively. These differences were not statistically significant (ANOVA, P = 0.05) and, therefore, it was concluded that the use of municipal wastes had similar effects on dry biomass production with that of conventional fertilization. An earlier harvest (125 days after plant emergence) gave 11.3% lower dry biomass on average in relation to the second harvest, and this difference was statistically significant (ANOVA, P = 0.05). Premature harvest may lead to significant biomass losses, so the plant must be collected during its technological maturity stage. There was not any statistically significant difference among the four treatments and between the two harvests in fiber dimensions and derived values (suitability indices for paper manufacture). On the other hand, cellulose and lignin content in the second harvest were significantly higher compared to the first one, whereas no significant differences were detected among the four treatments. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Kenaf (Hibiscus cannabinus L.) is an annual, dicotyledonous, herbaceous plant cultivated for its fibers; it has traditionally been grown throughout the west part of Asia for the manufacture of ropes, nets, carpets and sacks, and was selected by the USDA among 500 other species as one of the most promising source for pulp and paper production (Kugler, 1988). Kenaf pulps are suitable for the manufacture of newsprint and other paper products and are comparable in quality to hardwood and softwood pulps (Ayerza & Coates, 1996). In view of the shortage of conventional raw materials and the increasing demand for paper products in the European Union, kenaf ∗ Corresponding author. Present address: Ministry of Environment and Energy, Directorate of Environmental Planning, Biodiversity and Protected Areas Section. 147, Patision St., Athens GR 112 51, Greece. Fax: +30 210 8662024. E-mail addresses: bverv@dictyon.net, bverv@yahoo.gr (C. Ververis). cultivation has attracted renewed interest, especially in Mediter- ranean countries like Spain, Italy and Greece. There have been some experimental kenaf cultivations in Greece, which have shown that the plant can successfully adapt to local pedoclimatic condi- tions and give satisfactory (dry matter) yields ranging from 7 to 23 t/ha (Kosmidou-Dimitropoulou et al., 1991; Kipriotis et al., 1998; Alexopoulou et al., 2000). In 2012, Greece imported paper pulp and products at a cost of about D 850 million (Globaledge Statistics, 2012). It is, therefore, evident that new, domestic sources of pulp and paper raw materials would not only reduce imports but also would provide an economic incentive to the agricultural and the industrial sector of the country especially in an era of a serious economic crisis. To our knowledge and despite the fact that a lot of research has been done on the farming practices of kenaf cultivation, lit- tle experimentation to grow kenaf by using byproducts (sludge and wastewater) from Sewage Treatment Plants (STP) has taken place (Carlson et al., 1982; Webber, 1992). There are some studies in Greece on the effect of sewage sludge and wastewater use on the http://dx.doi.org/10.1016/j.indcrop.2016.01.040 0926-6690/© 2016 Elsevier B.V. All rights reserved.